Method of eradicating internal parasites

ABSTRACT

A method of treating warm blooded animals to eradicate certain internal parasites; which method comprises administering to said warm blooded animals a therapeutic dose of a composition comprising as active ingredient a compound of formula I ##EQU1## wherein X is halogen, and R 1  and R 2  which may be the same or different are selected from the group consisting of hydrogen, alkyl containing from 1 to 6 carbon atoms, -- NHR 3  where R 3  is hydrogen or an alkyl group containing from 1 to 6 carbons atoms; and when either R 1  or R 2  is -- NHR 3  then R 2  or R 1  respectively is hydrogen.

This invention relates to compositions for killing internal parasites ofwarm blooded animals; in particular it relates to compositions forkilling trematodes or nematodes. An example of a trematode is the liverfluke (Fasciola hepatica) which is a parasite of bile ducts of the liverof ruminants, such as cattle, sheep and goats. The liver fluke each yearcauses a significant amount of economic loss, not only from the death ofthe host animal but also from the deterioration in the value of meat andwool produced by infected animals. In cattle a loss in milk yield fromliver fluke infection will also occur and in addition the loss sustainedby the condemnation of infected livers as human food may also beconsiderable.

An example of a nematode is Haemonchus contortus which is a nematodeparasitic in the abomasum or fourth stomach of ruminants. It is a bloodsucking parasite and when present in large numbers can cause anaemia andfinally the death of the host. It can cause extensive losses, not onlyin the value of the animals which it may kill but also in the diminishedproduction of commercial items such as wool and meat. There is thereforea commercial need to treat animals with chemicals which are both safeand effective in reducing the incidence and severity of diseases causedby both trematodes and nematodes.

We have now found a class of compounds which are effective in killingliver fluke.

Accordingly we provide a method of treating warm blooded animals toeradicate certain internal parasites; which method comprisesadministering to said warm blooded animals a therapeutic dose of acomposition comprising as active ingredient a compound of formula I##STR1## wherein X is halogen, and R¹ and R² which may be the same ordifferent are selected from the group consisting of hydrogen, alkylcontaining from 1 to 6 carbon atoms, --NHR³ where R³ is hydrogen or analkyl group containing from 1 to 6 carbon atoms; and when either R¹ orR² is --NHR² then R² or R¹ respectively is hydrogen. Preferably X isfluorine, bromine or chlorine and R¹ and R² are hydrogen, or alkylcontaining from 1 to 3 carbon atoms. Most preferably the compound offormula I is monochloromethane sulphonamide.

The process of the present invention has utility in the field of animaltherapy. It is effective against both mature and immature liver fluke ofthe Fasciola genus. Many of the compositions also possess activityagainst nematodes such as Haemonchus contortus.

For effective treatment, certain dosage levels are desired dependingupon the compound employed, the type of animal to be treated, and theparticular helminth being combatted. In general, effective flukeefficacy is achieved when the composition is administered in a singledose at dosage levels of from about 25 to 200 mg active ingredient/kg ofanimal body weight, and preferably from about 50 to 100 mg activeingredient per kg of animal body weight.

The compositions of the present invention may be administered in avariety of ways, depending upon the particular animal employed, the typeof anthelmintic treatment normally given to such an animal, thematerials employed, and the particular helminths being combatted. It ispreferred to administer them in a single efficacious oral or parenteraldose at a time when fluke or nematode infection is apparent orsuspected. They may be employed alone or in combination with otheranthelmintics, parasiticides or antibacterials.

The amounts of the active anthelmintic ingredient in the composition, aswell as the remaining constituents are varied according to the type oftreatment to be employed, the host animal, and the particular parasiticdisease being treated. In general, however, compositions containing atotal weight percent of the active compound or compounds ranging from0.001 to 95% will be suitable with the remainder being any suitablecarrier or vehicle. Furthermore, the compositions should contain enoughof the active ingredient to provide an effective dosage for the propertreatment of the parasitic disease.

A number of modes of treatment may be employed, and each to some extentdetermines the general nature of the composition. For example, theanthelminthic compositions may be administered to domesticated animalsin single unit oral dosage form such as a tablet, bolus, capsule ordrench; in a liquid form suitable for parenteral administration; or theymay be compounded as a feed premix to be ater admixed with the animal'sfood.

When the compositions are to be solid unit dosage forms as in tablets,capsules, or boluses, the ingredients other than the active ingredientmay be any other pharmaceutically acceptable vehicles convenient in thepreparation of such forms, and preferably materials nutritionallysuitable such as starch, lactose, talc, magnesium stearate, vegetablegums, and the like. Moreover when capsules are employed, the activecompound may be used in essentially undiluted form, the only extraneousmaterial being that of the capsule casing itself which may be hard orsoft gelatin or any other pharmaceutically acceptable encapsulatingmaterial. When the dosage form is to be used for parenteraladministration, the active material is suitable admixed with anacceptable base vehicle. In all of such forms, i.e. in tablets, boluses,capsules, and injectable formulations, the active compound convenientlyranges from about 5 to 80% by weight of the total composition.

When the unit dosage form is to be in the form of a drench, the activeingredient may be mixed with agents which will aid in the subsequentsuspending of the active compound in water, such as bentonite, clays,water-soluble starch, cellulose derivatives, gums, surface active agentsand the like to form a dry predrench composition, and this predrenchcomposition added to water just before use. In the predrenchformulation, in addition to the suspending agent, such ingredients aspreservatives, antiform compounds, and the like may be employed. Such adry product may contain as much as 95% by weight of the active compound,the rest being contributed by the excipients. Preferably, the solidcomposition contains from 30% to 95% by weight of the active compound.Enough water should be added to the solid product to provide the properdosage level within a convenient amount of liquid for a single oraldose. Liquid formulations containing up to 70 weight percent of dryingredients will in general be suitable with the preferred range beingfrom 5 to 50 weight percent.

Where the compositions are intended to be used as feeds, feedsupplements, or feed premixes, they will be mixed with suitableingredients of an animal's nutrient ration. The solid orally-ingestiblecarriers normally used for such purposes, such as distillers' driedgrains, corn meal, citrus meal, fermentation residues, ground oystershells, Attapulgus clay, wheat shorts, molasses solubles, corn cob meal,edible vegetable substances, toasted dehulled soya flour, soybean millfeed, antibiotic mycelia, soya grits, crushed limestone and the like areall suitable. The active compounds are intimately dispersed or admixedthroughout the solid inert carrier by methods such as grinding,stirring, milling or tumbling. By selecting proper diluents and byaltering the ratio of carrier to active ingredient, compositions of anydesired concentration may be prepared. Feed supplement formulationscontaining from about 10 to 30% by weight of active ingredient areparticularly suitable for addition to feeds. The active compound isnormally dispersed or mixed uniformly in the diluent but in someinstances may be adsorbed on the carrier.

These supplements are added to the finished animal feed in an amountadequate to give the final concentration of active ingredient desiredfor controlling or treating the helminth infection by way of the animalration. Although the preferred level in feeds will depend on theparticular compounds being employed, the active ingredients of thisinvention are normally fed at levels of 0.05-25% in the feed. As statedabove, animals are preferably treated at a time when the infestation isapparent or suspected and the most preferred method for such treatmentis via the single dose technique. Thus administration of medicated feedis not preferred but may certainly be employed. Similarly, the amountsof drug present in the feed may be reduced to levels in the order of0.001% to 3.0 weight percent based on the weight of feed, and themedicated feed administered over prolonged periods. This would be in thenature of a preventive or propylactic measure but again is not the modeof choice. Another method of administering the compositions of thisinvention to animals whose feeds are conveniently pelleted, such assheep, is to incorporate them directly in the pellets. For instance, thecompositions are readily incorporated in nutritionally adequate alfalfapellets at levels of 2 to 110 grams per pound of pellets for therapeuticuse, and at lower levels for example 80 to 1000 milligrams per pound forprophylactic use, and such pellets fed to the animals.

Preferably the compositions are administered to the animal by parenteraldose and in a further aspect of our invention we provide an injectablecomposition comprising a sterile aqueous solution containing from 5 to70% w/w preferably 5 to 50% w/w of the active ingredient.

The composition may be sterilized by methods known to those skilled inthe art for the sterilization of injectable solution such as, forexample, ultra filtration or gamma radiation.

The compositions may also optionally contain other drugs of veterinaryutility. Veterinary drugs which may be present in the veterinarycompositions of this invention, depending upon the mode ofadministration of the said compositions, include for example,piperazine, 1-diethyl-carbamyl-4-methyl-piperazine, tetrachloroethylene,organic and inorganic arsenical compounds, tetramisole,2-phenyl-benzimidazole, thiabendazole, phenothiazine, mebendazole andpyrantel salts.

A particularly preferred composition according to our inventioncomprises an aqueous composition containing from 5 to 50% w/w of theactive ingredient of formula I and from 0.1 to 25% w/w of L-tetramisolefree base in the form of its acid salt, preferably the hydrochloride orphosphate salt. This composition is of use as a drench or, ifsterilized, as an injectable solution for treatment of warm bloodedanimals infected with a wide variety of helminths.

The invention is now illustrated by, but by no means limited to, thefollowing examples in which all parts are part by weight unlessotherwise specified.

EXAMPLE 1

A 5% aqueous solution of monochloromethanesulphonamide was prepared. Theactivity of this solution against adult Haemonchus contortus wasmeasured in the following way.

Three sheep which were known to be infected with Haemonchus contortuswere dosed as shown in Table I with the solution. One was dosed bysubcutaneous injection and two were dosed orally.

The effect on Haemonchus was measured initially by the change in therate at which eggs appeared in the faeces. Samples of faeces were drawnbefore dosing and at days 7 and 10 after dosing. The samples werehomogenised and diluted with water and the number of eggs per gram offaeces were assessed by standard procedure.

When the egg count showed a considerable reduction, the animal wasslaughtered and the stomach was examined for worms.

The results are shown in Table I. The dose refers to the activeingredient, monochloromethanesulphonamide.

                  TABLE I                                                         ______________________________________                                        Dose              Faecal Egg Count Worms                                      rate  Route of    on Day shown     present at                                 mg/kg Administration                                                                            0        7     10    P.M.                                   ______________________________________                                        100   Subcutaneous                                                                              5,600    0     0     0                                       50   Oral        8,400    2,000 1,500 Not killed                             100   Oral        40,000   0     0     0                                      ______________________________________                                    

EXAMPLE 2

The activity of a 5% aqueous solution of monochloromethanesulphonamideagainst adult Fasciola hepatica was measured in the following way.

Three sheep which were known to be infected with adult Fasciola hepaticawere dosed as shown in Table II with the solution. One sheep was dosedby subcutaneous injection and two were dosed orally.

The effect on Fasciola was measured initially by the change in the rateat which eggs appeared in the faeces. Samples of faeces were drawn justbefore dosing and 4, 7 or 10 days after dosing. The samples werehomogenised and diluted with water and the number of eggs per gram wereassessed by standard procedures.

At the end of day 10, all sheep were slaughtered and the bile ducts wereexamined carefully for the presence of adult fluke.

The results are shown below in Table II. Dose rates refer to the activeingredient, monochloromethanesulphonamide.

                  TABLE II                                                        ______________________________________                                        Dose               Faecal Egg Count Worms                                     rate   Route       on Day shown     present                                   mg/kg  Administration                                                                            0       4    7    10   at P.M.                             ______________________________________                                         60    Subcutaneous                                                                              360     0    --   --   0                                   100    Oral        1,800   --    10       0                                   100    Oral        460     --   110  0    --                                  ______________________________________                                    

EXAMPLE 3

A 45% aqueous solution of monochloromethanesulphonamide was prepared.The activity of this solution against adult Haemonchus contortus wasmeasured in the following way.

Nineteen sheep which were known to be infected with Haemonchus contortuswere dosed as shown in Table III with the solution. Fifteen were dosedby subcutaneous injection and four were dosed orally.

The effect on Haemonchus was measured initially by the change in therate at which eggs appeared in the faeces. Samples of faeces were drawnbefore dosing at at days 7 and 10 after dosing. The samples werehomogenised and diluted with water and the number of eggs per gram offaeces were assessed by standard procedure.

When the egg count showed a considerable reduction, the animal wasslaughtered and the stomach was examined for worms.

The results are shown in Table III. The dose refers to the activeingredient, monochloromethanesulphonamide.

                  TABLE III                                                       ______________________________________                                        Dose                                                                          rate   Route   Faecal egg count                                               mg/kg  *       Day 0    Day 7  P.M. result                                    ______________________________________                                        20     S/C      6,400   2,200  Not killed                                     20     S/C     45,00    5,600  "                                              20     S/C     15,000   11,400 "                                              20     S/C      8,800   1,300  "                                              40     S/C      9,000   1,400  "                                              40     S/C     12,200   5,600  970   H. contortus                             40     S/C     10,200   1,600  620   "                                        40     S/C     12,000   600    260   "                                        60     S/C      4,400   200    0     "                                        60     S/C      9,200   200    140   "                                        60     S/C     23,800   0      0     "                                        60     S/C     11,800   0      0     "                                        60     S/C      4,000   0      0     "                                        60     S/C     10,800   0      9     "                                        60     Oral     4,600   300    230   "                                        60     Oral     3,200   600    20    "                                        100    S/C     14,200   0      0     "                                        100    Oral    18,000   0      0     "                                        100    Oral    12,200   0      0     "                                        ______________________________________                                         * S/C subcutaneous injection?                                            

EXAMPLE 4

The activity of a 45% aqueous solution of monochloromethanesulphonamideagainst adult Fasciola hepatica was measured in the following way.

Nine sheep which were known to be infected with adult Fasciola hepaticawere dosed as shown in Table IV with the solution. Seven sheep weredosed by subcutaneous injection and two were dosed orally.

The effect on Fasciola was measured initially by the change in the rateat which eggs appeared in the faeces. Samples of faeces were drawn justbefore dosing and 4, 7 or 10 days after dosing. The samples werehomogenised and diluted with water and the number of eggs per gram wereassessed by standard procedures.

At the end of day 10, all sheep were slaughtered and the bile ducts wereexamined carefully for the presence of adult fluke.

The results are shown below in Table IV. Dose rates refer to the activeingredient, monochloromethanesulphonamide.

                  TABLE IV                                                        ______________________________________                                        (Liver Fluke (adult worms)                                                    Dose                                                                          rate   Route    Faecal Egg Count                                              mg/kg  *         Day 0     Day 10  P.M. result                                ______________________________________                                        100    Oral     1,800      0       0 fluke                                    100    Oral     460        100     0 fluke                                    75     S/C      280        0       0 fluke                                    75     S/C      350        0       0 fluke                                    60     S/C      360         50     0 fluke                                    50     S/C      470         40     69 fluke                                   50     S/C       30        0       14 fluke                                   25     S/C       70        120     Not killed                                 25     S/C      280        520     Not killed                                 ______________________________________                                         * S/C subcutaneous injection                                             

EXAMPLE 5

The activity of a 45% aqueous solution of monochloromethanesulphonamideagainst immature forms of Fasciola hepatica of various ages was measuredin the following way:

Each animal in a group of fluke-free sheep was infected with a similarvolume of a suspension of metacercariae containing from 200 to 500metacercariae. The animals were divided into several groups eachcontaining 6 sheep -- some were untreated (control group) and otherswere treated with various doses of the test chemical at different timesafter infection. In this way the age of the fluke at the time of dosingcould be established.

After treatment the infection was allowed to develop to maturity (atleast 11 weeks from infection); the animals were then killed and all thefluke in the liver were collected and counted. The average number offluke surviving the treatment in each group of animals was compared withthe average number in the control group. In this way the degree ofcontrol was calculated (expressed as a percentage kill).

The results are summarized in Table V.

                  TABLE V                                                         ______________________________________                                        Age of fluke  Dose                                                            (weeks)       (mg/kg)       % kill                                            ______________________________________                                        2             100           100                                               3             100           86                                                6              75           28                                                6             100           49                                                6             150           93                                                ______________________________________                                    

EXAMPLE 6

An aqueous solution containing 45% w/w monochloromethane sulphonamideand 6.8% w/w levamisole free base in the form of the hydrochloride saltwas prepared. The solution was sterilized by filtration through abiological filter.

A steer of approximately 200 kg bodyweight was dosed by subcutaneousinjection with 45 mls of the sterilized solution. On inspection 24 hoursafter injection only minor tissue reaction was observed at the injectionsite.

EXAMPLE 7

A 500 lb cow infested with Fasciola was dosed at 100 mg/kg ofmonochloromethanesulphonamide and 8 mg/kg levamisole hydrochloride withthe following sterilized solution.

    ______________________________________                                        Cl--CH.sub.2 --SO.sub.2 NH.sub.2                                                                 45 % w/v                                                   Levamisole HCl     3.6% w/v                                                   NaH.sub.2 PO.sub.4 2 H.sub.2 O                                                                   2.0% w/v                                                   Citric Acid        2.4% w/v                                                   Water to 100 vols                                                             ______________________________________                                    

The dose was 10 ml of the above solution/100 lb bodyweight. This wasgiven as 2 × 25 ml doses over the rib area.

Palpation of the injection sites for up to 14 days post treatmentrevealed only minor subcutaneous thickening and no observable lump orswelling. On post mortem examination 24 days post injection some yellowdiscolouration of the subcutaneous tissue over the subcutaneous musclewas apparent but this did not penetrate the muscle. There was nonecrosis, fibrosis or oedema and after the carcass had cooled down thediscolouration was barely recognizable.

There were no liver fluke found on post mortem.

EXAMPLE 8

A mixture was prepared consisting of

    ______________________________________                                        Cl--CH.sub.2 --SO.sub.2 NH.sub.2                                                            45% w/v                                                         Levamisole phosphate                                                                        equivalent 3.6% w/v of levamisole                                             HCl                                                             NaH.sub.2 PO.sub.4 2 H.sub.2 O                                                              2.0% w/v                                                        Citric Acid   2.4% w/v                                                        Water to 100                                                                  ______________________________________                                    

The solution was sterilized by filtration.

Two cows weighing between 1000 and 1100 lbs infested with Fasciola wereinjected with 60 mls of the sterilized mixture in the middle of the leftside over the last two ribs. The animals were slaughtered after 28 daysand after skinning only a very faint blemish was observed at theinjection site. No liver fluke were found on post mortem.

In parallel with the above two further cows weighing between 1000 and1100 lbs were similarly injected with 37.5 mls of the solution. Similarresults were obtained on post mortem.

EXAMPLE 9

A series of sulphonamides were tested for flukicidal activity in thefollowing manner.

An aqueous solution of the test compound was sterilized by filtrationand used as either a subcutaneous injection or an oral drench to dosesheep known to be infected with adult Fasciola hepatica. The effect onFasciola was measured by the method of Example 2. The results are shownbelow in Table VI.

                                      TABLE VI                                    __________________________________________________________________________    Dose rate                                                                     mg/kg                                                                         bodyweight                                                                    and mode of       Faecal egg count  Worms                                     administra-       on days shown     present                                   tion   Test Compound                                                                            0   4   7   10 15 at P.M.                                   __________________________________________________________________________    70 oral                                                                              I--CH.sub.2 --SO.sub.2 NH.sub.2                                                          450 --   30 --    --                                        50 S/C Br--CH.sub.2 --SO.sub.2 --NHEt                                                           260 --  180 -- 0  0                                         50 S/C Br--CH.sub.2 --SO.sub.2 NH.sub.2                                                         230 240 0   0     0                                         50 S/C Cl--CH.sub.2 --SO.sub.2 NHEt                                                             760 --  0   0     0                                         40 oral                                                                              Cl--CH.sub.2 --SO.sub.2 N(Et).sub.2                                                      130 --  0   --    0                                         50 oral                                                                              F CH.sub.2 SO.sub.2 NH.sub.2                                                             265 --  245 -- 0  --                                               (in admixture                                                                 with FCl CH                                                                   SO.sub.2 NH.sub.2                                                      __________________________________________________________________________

We claim:
 1. A method for treating warm blooded animals to eradicateFasciola sp and Haemonchus contortus; which method comprisesadministering internally to said warm blooded animals an effectiveamount of a composition comprising as active ingredient a compound offormula I ##EQU2## wherein X is halogen, and R¹ and R² which may be thesame or different are selected from the group consisting of hydrogen andalkyl of from 1 to 6 carbon atoms.
 2. The method of claim 1 wherein X isfluorine, bromine or chlorine.
 3. The method of claim 1 wherein R¹ andR² which may be the same or different are hydrogen or alkyl containing 1to 3 carbon atoms.
 4. The method of claim 1 wherein the activeingredient is monochloromethanesulphonamide.
 5. The method claim 1wherein the composition is administered in a single dose at dosagelevels of from about 25 to 200 mg active ingredient/kg of animal bodyweight.
 6. The method of claim 5 wherein the single dose is at dosagelevels of from 50 to 100 mg active ingredient per kg of animal bodyweight.
 7. The method of claim 1 wherein said composition is a sterileaqueous solution containing from 5 to 70% w/w of the active ingredientand said composition is administered by injection.
 8. The method ofclaim 7 wherein the composition comprises from 5 to 50% w/w of activeingredient.
 9. The method of claim 7 wherein the composition comprisesfrom 5 to 50% w/w of active ingredient, and from 0.1 to 25% w/w ofL-tetramisole free base in the form of its acid salt.
 10. The method ofclaim 7 wherein the composition comprises from 5 to 50% w/w ofmonochloromethane sulphonamide and from 0.1 to 25% w/w of L-tetramisolehydrochloride or phosphate.